1. Field of the Invention
The present invention relates to a method and instrumentation for detecting, locating and diagnosing automotive chassis sounds. More particularly, the invention is directed to electronic diagnostic instrumentation for locating the source and cause, in automotive vehicles, of under-chassis, under-hood and under-dash problem sounds and noise. The instrumentation is most suitable for use by automotive repair and service personnel.
2. Description of The Prior Art
The modern automotive vehicle, whether a passenger automobile, recreational vehicle, pick-up truck, delivery van or large semitrailer, presents a complex conglomeration of engine, power transmission, differential, wheels and bearings, and associated machinery and devices that each present a potential for problems with the resulting generation of vibrations, sounds and noise. Today's automotive vehicle manufacturers stress that their driver and passenger compartments are "sound proof" and this factor multiplies the problem of locating under-chassis, under-hood and under-dash mechanical sounds and noise (including squeaks and rattles) generated by faulty and improperly functioning automotive machinery and parts.
It has been well known to use mechanical vibration detectors as a means for determining whether, or where it is, that an automotive vehicle needs repair or adjustment to assure optimum operation. One such device, called a "Vibrameter," has been manufactured by SPM Instrument, Inc. of Wallingford, Conn. and includes a piezoelectric device attached to a vibrating automotive part and converts the vibrations to an electrical signal in digital form that is displayed on a hand-held device. Another similar device, also manufactured by SPM Instrument, Inc., is called the "Electronic Stethoscope" and includes a hand-held device having an elongated probe capable of being placed against a vibrating machine part and connected through a piezoelectric unit for converting the detected vibrations into an electrical signal which is amplified through earphones so that the vibrations are detected as a noise level.
In December of 1988, U.S. Pat. No. 4,790,191 was granted to W.L. Shultz, Jr. for "Comparative Mechanical Fault Detection Apparatus and Clamp." The Shultz patent is directed to apparatus for determining a mechanical fault in an automotive vehicle by determining mechanical vibration comparatively between two like devices of the vehicle to determine which of the two devices is in need of repair or replacement. The apparatus includes two piezoelectric vibration sensors operatively secured to a pair of mechanical clamps capable of being attached to two like devices of the vehicle such as a pair of McPherson struts interconnected through metal parts to two front wheel bearing assemblies. The first and second piezoelectric sensors are operatively and alternatively connected electrically to an indicator device for producing an electrical signal amplitude proportional to mechanical vibration whereby the operator of the apparatus can audibly hear (via a speaker or through earphones) the differences in vibration amplitude between the two like devices and determine which of the devices has a mechanical fault.
In 1989, JS Products, Inc. of Las Vegas, Nev. introduced to the automotive maintenance and repair field the "ChassisEAR" as an electronic squeak and rattle finder. This device includes six sensitive piezoelectric microphones mounted in alligator-type clamps available for attachment to a variety of vehicle devices and structural points where excessive vibration may be suspected as an indication of mechanical problems. Electrical leads from the individual clamps are connected to a control box which includes vibration signal conversion circuitry for producing audible signals. The control box also includes switching means for selectively interconnecting each individual clamp microphone to the signal conversion circuitry and thereby selective connection to earphones for use by automotive repairmen in determining through audible signal levels and signal types the location and cause of problem-generated automotive sounds and noises.
It is a principal object of the present invention to provide a new and improved vibration and acoustic sound diagnostic tool for the professional automotive maintenance field to detect with greater sensitivity and accuracy the existence, location and cause of under-chassis, under-hood and under-dash problem sounds and noise.
It is a further object of the invention to provide a new and improved electronic listening tool for the professional automotive mechanic which is capable of discriminating with greater sensitivity abnormal acoustic vibratory signals and sounds forming the noise patterns of automotive vehicle structures and operating parts having mechanical problem faults and to locate the source and cause of such abnormal signals and sounds during normal driving movement of the vehicle.
It is a still further object of the invention to provide a new and improved vibration and acoustic sound diagnostic instrument, with multiple vibration pick-up devices positional for direct contact with under-chassis and under-hood automotive vehicle parts and devices, for locating the source and cause of mechanical problem faults related to such parts and devices, the pick-up devices being coupled through electronic circuitry to an earphone headset for audible vibration sound discrimination and to visual means for indicating changes and peaks in vibration sound level and average values of vibration sound level.
Other objects and advantages of the invention will be apparent to those skilled in the professional automotive maintenance field from the following summary and detailed description of the acoustic vibratory signal and sound diagnostic instrument of the invention taken together with the accompanying drawing figures.